An intensive program has been followed to characterize the sequence and mechanism of human lymphocyte responsiveness to specific antigen in vitro within the blastogenesis system. Towards this end, development and application of automated laser cytometry to this assay was carried out. Laser cytometry was found to allow for a fuller characterization of the nature of immune responsiveness within this assay of cell associated immunity. In addition, the biologic effect of hormonal agents (adrenergic stimulators (agonists) and blockers) on antigen stimulated immune response was studied. BIBLIOGRAPHIC REFERENCES: Ruckdeschel, J.C., Doukas, J.G., Drake, W.P., and Mardiney, M.R., Jr.: Application of Laser Cytometry to the Analysis of Immunologically Induced In Vitro Lymphocyte Responsiveness. Transplantation 23: 396-403, 1977. Doukas, J.G., Ruckdeschel, J.C., and Mardiney, M.R., Jr.: Quantitative and Qualitative Analysis of Human Lymphocyte Proliferation to Specific Antigen in Vitro by Use of the Helium Neon Laser. J. Immunol. Methods 15: 229-238, 1977.